We are undertaking a study to evaluate the genetic basis of prostate cancer. In particular, we are studying brothers where at least one has prostate cancer in order to investigate the potential relation between genetic factors and their disease. The brothers will be primarily recruited into the study through registries at Case Western Reserve University, the Cleveland Clinic Foundation, the Henry Ford Health System, MetroHealth Medical Center, and University Hospitals of Cleveland. More specifically, we are contacting men who have been diagnosed with prostate cancer at these institutions to see if they have brothers and whether they would be willing to join our study. Since we are focusing on genetic factors, at this time we are only contacting those men who were aged 70 or younger when they were diagnosed (their brothers can be any age). We are collecting blood from the men, as well as basic information on their health, habits and diet. From the blood we will get DNA, and then use this information to look at those genes that plausibly could lead to prostate cancer, based on current scientific evidence. In particular, we will study whether brothers who have prostate cancer inherit certain forms of the genes more often than expected by chance, and whether such forms of these genes are associated with the aggressiveness of prostate cancer. If so, this implicates such genes in the development and/or aggressiveness of prostate cancer. The information from this study will help provide men with additional knowledge about their risk of prostate cancer and, if they are already diseased, how genes might influence their response to treatment. )